The present invention relates to a transparent conductive laminate and to a touch panel which uses the transparent conductive laminate and has excellent durability and excellent visibility.
Recently, the wide employment of portable information-processing equipment on which a liquid crystal display for displaying information and a touch panel (called a switch panel, a membrane switch or a tablet) for inputting information were loaded was started. Most of the touch panels are resistant film type ones. Each of the resistant film type touch panel is formed by facing two transparent electrode substrates having transparent conductive layers formed thereon, respectively, each other at a distance of 10 to 100 xcexcm. Both the transparent electrode substrates are brought into contact with each other only at a site touched by a finger, a pen, or the like, to act as a switch. For example, the selection of a menu on a display screen, the inputting of a handwritten figure, handwritten letters, or so on, can be carried out. As the transparent electrode substrates, ones manufactured by disposing the transparent conductive layers of a metal oxide such as indium tin oxide (ITO) or tin oxide containing antimony or the like on substrates such as glass substrates or various kinds of transparent polymer substrates are widely used.
In the touch panel, the transparent electrode substrate on the side to be touched by the finger, the pen, or the like (movable electrode substrate), is preferable to be flexible from a point that the figure, letters, or the like, can easily be inputted. As the movable electrode substrate, an electrode substrate obtained by disposing a transparent conductive layer on a transparent polymer film substrate or a transparent polymer sheet substrate is usually used. There has been a problem that, when a flexible transparent electrode substrate is used as a movable electrode substrate, the movable electrode substrate is loosened due to the changes of temperature and humidity, resulting in the generation of interference fringes between the movable electrode substrate and the facing fixed electrode substrate to give an indistinct screen. There has also been a problem that, when both the surface of a movable electrode substrate and the surface of a fixed electrode substrate are extremely flat, the electrode surface of the movable electrode substrate and the electrode surface of the fixed electrode substrate are adhered to each other to cause the failure in the operation of the touch panel.
In order to solve the problems, the present inventors proposed a method for making the surface of an electrode with micro bumps. In JP-A No. 8-216327 (1996) (hereunder, JP-A means Japanese unexamined patent publication) is described a touch panel that the generation of interference fringes was controlled by using a transparent conductive laminate whose transparent conductive layer surface has a central surface average roughness (SRa) of 0.05 to 0.40 xcexcm. In JP-A No. 10-24516 (1998) is also described a transparent conductive laminate which uses silicone resin fine particles having an average particle diameter of 4.5 xcexcm and has an excellent slipping property and whose transparent conductive layer surface has a central surface average roughness (SRa) of 0.003 to 0.04 xcexcm. Thereby, the problems of the generation of interference fringes and of the mutual adhesion of electrode surfaces were solved, but writing durability was often insufficient. Namely, when a test for the writing durability was carried out, it was found that the peeling of the transparent conductive layer was sometimes caused on the peripheries of the electrode surface bumps of a movable electrode substrate, resulting in the deterioration of the inputting performance of the touch panel (for example, the generation of misprinting, the insufficient accuracy of position detection) after the test of the writing durability.
On the other hand, a transparent conductive laminate in which a coating layer containing fine particles was disposed between a transparent plastic film and a transparent conductive layer was proposed for improving the writing durability (JP-A No. 10-249975 (1998)). According to the description of the patent publication, the damages of the transparent conductive layer were concentrated at extremely small areas around the apexes of bumps, because the bumps were distributed on the surface of the electrode at a proper density. Consequently, even when the transparent conductive layer was damaged, the total resistance of the transparent conductive layer was largely not changed, and the accuracy of position detection was scarcely changed. Further, the good average particle diameter of fine particles contained in the coating layer was in the range of from not less than the thickness of the coating layer to three times or less than that of the coating layer, and the good density of the particles was 10,000 to 500,000 particles/cm2 (100 to 5,000 particles/mm2). However, the examinations of the present inventors showed that the writing durability was always not improved, even when the density of the particles was set to the range.
Further, in JP-A No. 10-323931 (1998) is described a transparent conductive laminate in which a coating layer containing particles having an average particle diameter of 1.0 to 4 xcexcm at a number-average density of 500 to 3,000 particles/mm2 and a transparent conductive layer were successively formed on a transparent plastic film to control the generation of interference fringes. However, the transparent conductive layer surface of the laminate had a ten point height (Rz) of 0.3 to 1.0 xcexcm or larger, therefore comprised bumps of large dispersion of height, and the writing durability of the laminate was insufficient, when used as a touch panel.
A main object of the present invention is to provide a transparent conductive laminate suitable for giving a touch panel having excellent writing durability.
Another object of the present invention is to provide a touch panel which has good writing durability and excellent visibility.
The present inventors have paid attentions on the heights of bumps on the surface of a transparent conductive layer and have researched to solve the above-mentioned problems and obtain the touch panel which scarcely generates interference fringes and has excellent visibility giving clear letters and excellent writing durability.
Consequently, the present inventors ascertained that the writing durability did essentially not depend on the density of fine particles and that the existence of bumps, which are higher than a certain height, especially caused a problem, when the surface of a transparent conductive layer used as the electrode of the touch panel had high bumps and low bumps in a mixed state especially of large dispersion of height.
On the other hand, since adhesivity between the transparent conductive layer and a substrate such as a polymer film was also important for dynamic mechanical durability called the writing durability, the present inventors further repeatedly researched the point. It was consequently found that a peeling was caused between the transparent conductive layer and a layer containing fine particles, when the layer containing fine particles was disposed just under the transparent conductive layer in a state directly contacted with the transparent conductive layer. The inventors also examined the point and in consequence found out that it was important to control the height of bumps and the density of bumps in the layer containing fine particles and that it was extremely effective to dispose a cross-linked polymer layer between the layer containing fine particles and the transparent conductive layer in a state contacted with the transparent conductive layer.
The present invention was completed by repeating the researches on the basis of the knowledge. Namely, the present invention relates to the transparent conductive laminate which is obtained by controlling the height of the bumps and the density of the bumps in the surface of the transparent conductive layer, controlling the height of the bumps and the density of the bumps in the surface of the layer containing fine particles between the transparent conductive layer and the substrate, and disposing the cross-linked polymer layer in the state contacting with the transparent conductive layer, and is especially useful for a touch panel.
Namely, the present invention is as follows.
A transparent conductive laminate comprising a transparent polymer substrate and a transparent conductive layer disposed on at lo least one of sides of the transparent polymer substrate, the transparent conductive layer has a outer surface containing micro bumps, wherein:
the transparent conductive laminate comprises a cross-linked polymer layer (A) containing fine particles and a cross-linked polymer layer (B) between the transparent polymer substrate and the transparent conductive layer, said cross-linked polymer layer (A) is between the transparent polymer substrate and the cross-linked polymer layer (B); the cross-linked polymer layer (B) contacts the transparent conductive layer; and the outer surface of said transparent conductive layer comprises the bumps having an average height of 0.3 to 1 xcexcm and a density in the range of 350 to 1,800 bumps/mm2.
The transparent conductive laminate wherein the cross-linked polymer layer (A) has a surface facing the cross-linked polymer layer (B), said surface comprises micro bumps having an average height of 0.3 to 1 xcexcm and a density of 350 to 1,800 bumps/mm2.
The transparent conductive laminate wherein the cross-linked polymer layer (B) is 20 to 110 nm in thickness.
The transparent conductive laminate wherein the cross-linked polymer layer (A) comprises a radiation-cured acrylic resin.
The transparent conductive laminate wherein the fine particles have an average diameter of 2 to 4 xcexcm.
The transparent conductive laminate wherein the cross-linked polymer layer (B) does not contain fine particles substantially.
The transparent conductive laminate wherein the cross-linked polymer layer (B) is obtained by hydrolyzation and condensation polymerization of a metal alkoxide.
The transparent conductive laminate wherein the transparent polymer substrate is a film or sheet of a thermoplastic polymer.
The transparent conductive laminate wherein the transparent conductive layer comprises mainly a metal oxide.
A transparent conductive laminate comprises a transparent polymer substrate and a transparent conductive layer, said transparent polymer substrate is a thermoplastic polymer film or sheet, said transparent conductive layer comprising mainly a metal oxide, wherein the transparent conductive layer is disposed on one of sides, and the transparent conductive layer has a surface containing micro bumps, further wherein: (1) the transparent conductive laminate comprises, between the transparent polymer substrate and the transparent conductive layer, a radiation-cured resin layer (A1) which comprises an acrylic resin containing fine particles having an average diameter of 2 to 4 xcexcm, and a cross-linked polymer layer (B1) which does not containing fine particles substantially and obtained by hydrolyzation and condensation polymerization of a metal alkoxide, said radiation-cured resin layer (A1) is disposed between said transparent polymer substrate and the cross-linked polymer layer (B1); (2) the cross-linked polymer layer (B1) has 20 to 110 nm in thickness and contacts with the transparent conductive layer; and (3) the transparent conductive layer has a surface containing micro bumps having an average height of 0.3 to 1 xcexcm and a density of 350 to 1,800 bumps/mm2.
The transparent conductive laminate further comprises a cross-linked polymer layer (C) disposed between the cross-linked polymer layer (A) containing fine particles and the cross-linked polymer layer (B), said cross-linked polymer layer (C) has a higher refractive index than that of the cross-linked polymer layer (B).
The transparent conductive laminate wherein the transparent conductive layer has a surface having an average reflectance of not more than 5.5% in wavelength of 450 to 650 nm and a b* value of transmitted light being xe2x88x922 to +3, wherein the b* value is obtained based on psychometric chroma coordinates in the CIE 1976 (L*a*b*) Space according to Japan Industrial Standard No. Z8729.
The transparent conductive laminate wherein the cross-linked polymer layer (C) has a refractive index at least 1.7 and not more than that of +0.3 higher than the refractive index of said transparent conductive layer, and has 20 to 90 nm in thickness; the cross-linked polymer layer (B) has 1.35 to 1.5 in refractive index and 30 to 110 nm in thickness; the transparent conductive layer has 12 to 30 nm in thickness; and the cross-linked polymer layer (C), the cross-linked polymer layer (B) and the transparent conductive layer have 180 to 230 nm in total of optical path length of each layer (wherein the optical path length is a value obtained by multiplying a refractive index of a layer with a thickness of the layer).
The transparent conductive laminate wherein the cross-linked polymer layer (C) and the cross-linked polymer layer (B) are cross-linked polymer layers obtained by mainly hydrolyzation and condensation polymerization of metal alkoxides, respectively.
The transparent conductive laminate wherein the cross-linked polymer layer (C) has a refractive index in a range of 1.7 and +0.3 higher than the refractive index of the transparent conductive layer; the cross-linked polymer layer (B) has 1.35 to 1.5 in refractive index; the transparent conductive layer has 12 to 30 nm in thickness; and the polymer layer (B) has a minimum point of surface reflectance within a wavelength range between 260 and 390 nm.
The transparent conductive laminate wherein the cross-linked polymer layer (C) and the cross-linked polymer layer (B) are cross-linked polymer layers obtained by mainly hydrolyzation and condensation polymerization of metal alkoxides, respectively.
A touch panel comprising two transparent electrode substrates, each of which has a conductive layer at least one side of the substrate and the transparent conductive layers of the two substrates face each other, characterized in that at least one of the transparent conductive substrates is the transparent conductive laminate according to claim 1.
The touch panel further comprises a transparent polymer film or sheet being laminated to a side opposite to the side where the transparent conductive layer of the transparent conductive laminate is formed.